CN108152680A - Method for detecting commutation failure of direct-current transmission - Google Patents
Method for detecting commutation failure of direct-current transmission Download PDFInfo
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- CN108152680A CN108152680A CN201711477615.3A CN201711477615A CN108152680A CN 108152680 A CN108152680 A CN 108152680A CN 201711477615 A CN201711477615 A CN 201711477615A CN 108152680 A CN108152680 A CN 108152680A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention discloses a method for detecting a direct current transmission commutation failure, which adopts Daubechies wavelet with second-order moment of disappearance to analyze by collecting the characteristics of direct current waveforms before and after the commutation failure, thereby eliminating the normal state and slight faults of an alternating current system and achieving the purpose of quickly detecting the time point of the commutation failure. The method has the advantages of simple calculation process, high calculation speed and high detection precision in the detection process of the commutation failure of the direct-current transmission system, can be applied on line, is convenient for accurately detecting the commutation failure, can quickly obtain commutation failure information, avoids the failure of a transmission line and equipment of a converter station, and improves the operation safety of a power grid.
Description
Technical field
The present invention relates to transmission system commutation detection field, particularly a kind of method for detecting direct current transportation commutation failure.
Background technology
D.C. high voltage transmission (High Voltage Direct Current, HVDC), for improving existing electric system
Transmittability excavates existing equipment potentiality, is of great practical significance, and is the power transmission mode that country greatly develops.
The transverter of HVDC systems is in interior commutation of each period (0.02 second) 6 times, after commutation between two bridge arms,
In a period of time that the firm valve for exiting conducting is acted in backward voltage, failing to restoring blocking ability or in backward voltage
Period commutation process fails to be finished always, and both of these case all will be to original by the valve of commutation when threshold voltage is changed into forward direction
Valve to make a reservation for exit conducting switches phase, this claims phenomenon to be known as commutation failure.Compared to rectification side, inverter side thyristor is born instead
Less to the time of voltage, the possibility that commutation failure occurs is much higher.Thyristor needs certain time completion carrier to answer
It closes, restores blocking ability, deionization recovery time is in 400 μ s (about 7 electrical angle) left and right.Commutation failure causes DC current
Become larger, threaten the insulation safety of transmission line of electricity and current conversion station equipment, cause the imbalance of alternating current circuit three-phase voltage, pacify for power grid
Row for the national games brings significant threat.
Detection method currently used for DC transmission system commutation failure is broadly divided into two classes：When actual measurement type, it will be each
A valve electric current finish time is converted into angular metric to obtain blow-out angle with the time interval of corresponding commutation voltage zero-acrross ing moment, and then
It is compared with limit blow-out angle and judges whether that commutation failure occurs；Second is that forecasting type, utilizes change of current busbar electricity in AC fault
Pressure judges whether exchange side failure may cause commutation failure.Both institutes are insufficient, and actual measurement type method is based on experience conclusion, will
Blow-out angle testing result is relatively drawn a conclusion with limiting value, but blow-out angle is maximum probability less than limiting value rather than absolutely changes
To failure, therefore erroneous judgement may occur for actual measurement type method.Forecasting type is based on this transient state mistake of steady-state model analysis commutation failure
Journey, model precision existing defects itself, acquired results also disagree with practical.
Therefore, there are accuracy of detection is relatively low, commutation failure is difficult for the detection method of current DC transmission system commutation failure
The problem of accurately to detect, easily judge by accident, easily leads to the imbalance of alternating current circuit three-phase voltage, safety during operation of power networks
Hidden danger is larger.
Invention content
The object of the present invention is to provide a kind of methods for detecting direct current transportation commutation failure.The present invention is in direct current transportation
There is the advantages of calculating process is simple, and calculating speed is fast, and accuracy of detection is high in the detection process of system commutation failure, it can be online
Using accurately being detected convenient for commutation failure, can obtain commutation failure information rapidly, transmission line of electricity and current conversion station equipment is avoided to occur
Failure improves the safety of operation of power networks.
Technical scheme of the present invention：A kind of method for detecting direct current transportation commutation failure, this method is by acquiring direct current
Current sampling data is detected DC current sampled data, so as to judge the specific time point of direct-current commutation failure generation,
Achieve the purpose that be quickly detected the time point of commutation failure.
In a kind of method of aforementioned detection direct current transportation commutation failure, the method is sampled by acquiring DC current
Using DC current sampled data before and after commutation failure as foundation, according to DC current during commutation failure improper jump occurs for data
It rises, the second order and more than order derivative of current data have the feature significantly increased, using with second order vanishing moment
Daubechies small echos carry out Singularity Detection to DC current sampled data, and the method based on threshold value comparison judges direct current commutation
At the specific time point that failure occurs, reach and eliminate normal condition and AC system minor failure, be quickly detected commutation failure
Time point purpose.
Compared with prior art, by analyzing dc current waveform before and after HVDC system commutation failures the characteristics of, using tool
The Daubechies small echos for having second order vanishing moment are analyzed, and effectively eliminate normal condition and AC system minor failure
(failure that commutation failure does not occur) is quickly detected the time point of commutation failure, is dispatching of power netwoks and operations staff first
Time provides warning.
By taking the straight-flow system in Fig. 1 as an example, inverter side (right side) occurs before commutation failure in dc current waveform such as Fig. 3
It is with the straight line centainly fluctuated before the t0 moment；When three-phase ground failure (t0 moment), direct current occur for inverter side AC system
Electric current firstly because the reduction of DC voltage and become larger (t0-t1 periods), commutation failure not yet occurs at this time；The t1 moment occurs
Commutation failure (I2 represents that No. 2 valve waveforms of commutation failure occur in Fig. 3), No. 4 valves should be connected but because of commutation voltage at this time
Deficiency is closed in advance, and No. 2 valves are connected again, that is, commutation failure occurs, and with the normally of No. 5 valves, No. 2 and No. 5 valves are simultaneously
Conducting forms dc-side short-circuit, and DC current increases there are one apparent, with the slope increase of bigger and reaches peak in t2；This
Afterwards due to the effect of straight-flow system controller, current value reduces, but failure not yet excludes, and commutation failure occurs herein for the t3 moment
(in figure below of Fig. 3 I5 represent No. 5 valve (position of No. 5 valves please be indicated, in Fig. 2) current waveforms), should close but again in t3
Secondary conducting, i.e. 5 valves form direct-current short circuit for the second time to 1 valve commutation failure, 2-5 valves, and DC current mutates again；Hereafter by
In controller action, DC current persistently reduces, and follow-up commutation failure does not continue to occur.
Analysis shows, DC current has apparent transition before and after commutation failure generation at commutation failure point above,
By detecting these transition points, fast and accurately it can determine whether commutation failure occurs.Accordingly, the present invention is proposed to use and be had
The Daucechies small echos of 2 rank vanishing moments handle current sampling signal, judge commutation failure using each point wavelet coefficient
Whether occur.
For DC current there are ripple, there is second dervative non-zero in current waveform during system normal operation.Commutation is lost
It loses moment corresponding DC current to mutate, the feature of second dervative non-zero becomes apparent, and wavelet coefficient is compared with other moment
It is more prominent.In this regard, sampled to DC current, its high-order (second order and more than) derivative information is obtained, higher derivative is more than
Threshold value is believed that commutation failure.
Daubechies small echo Ψ (x) waveforms with 2 rank vanishing moments as shown in figure 4, the supported collection of the small echo for 0-3,
It carries out wavelet analysis to specially appointed kind progression f (x), and obtains wavelet coefficient Bk jFormula is as follows：
Wherein k represents the translational movement of data, and j represents resolution ratio.F on the right of (1) formula is carried out second order Taylor's decomposition, is had
Wherein O (2-jK) it represents higher derivative item, represents and then (1) formula can be expressed as
Since Ψ (x) has second order vanishing moment, so
Therefore result is related as the second dervative of ordered series of numbers f (X) shown in (1) formula.
Based on above analysis, using the Daubechies small echo Ψ (x) with 2 rank vanishing moments to dc current waveform Id into
Row analysis using the point that the point that wavelet coefficient is more than threshold value occurs as commutation failure, can quickly obtain commutation failure generation
Moment, while eliminate and the ordinary failures (t0-t1 periods, first derivative variation) of commutation failure and controller work do not occur
With the interference of point (t2), there is good application for the detection of direct-current commutation failure.
The selection principle of threshold value：According to formula (5), the size and DC current sample frequency and small echo letter of wavelet coefficient
Several data lengths is related.In this illustrates the corresponding examples of result displaying figure Fig. 5, DC current data come from EMTDC/
PSCAD simulation softwares, sample frequency 4000Hz, wavelet data length is 769, straight during straight-flow system normal operation under the conditions of this
Galvanic electricity stream sampled point maximum wavelet coefficient is 0.103.It is also had accordingly in view of the wavelet coefficient during non-commutation failure failure
Increase, it is that comparison is rational to consider lower 0.15 as threshold value.In practice, with reference to the sample frequency of system and small
The wavelet coefficient for more meeting engineering reality can be calculated by formula (5) for wavelength degree.
In conclusion the present invention has in the detection process of DC transmission system commutation failure, calculating process is simple, meter
The advantages of speed is fast, and accuracy of detection is high is calculated, can accurately be detected convenient for commutation failure with application on site, can show that commutation is lost rapidly
Information is lost, transmission line of electricity and current conversion station equipment is avoided to break down, improves the safety of operation of power networks.
Description of the drawings
Fig. 1 is straight-flow system and equivalent AC network schematic diagram；
Fig. 2 is change of current valve group position view in Inverter Station；
Fig. 3 is converter valve current waveform (upper figure No. 2 valve current waveforms of expression and the DC current wave before and after AC fault
Shape, figure below represent No. 5 valve current waveforms and DC waveform)；
Fig. 4 is the wavelet shapes that the present invention uses；
Fig. 5 is the testing result that three-phase ground failure causes commutation failure；
Fig. 6 is No. 2 valves and the current waveform of No. 6 valves and DC current when singlephase earth fault causes commutation；
Fig. 7 is the testing result of Fig. 6；
Fig. 8 is singlephase earth fault, and single fault degree is smaller, fails to draw testing result during direct-current commutation failure.
Specific embodiment
The present invention is further illustrated with reference to the accompanying drawings and examples, but be not intended as to the present invention limit according to
According to.
Embodiment.A kind of method for detecting direct current transportation commutation failure, as shown in Figures 1 to 5, this method is to pass through acquisition
DC current sampled data is detected DC current sampled data, so as to judge direct-current commutation failure occur it is specific when
Between point, achieve the purpose that be quickly detected the time point of commutation failure.
The method be by acquiring DC current sampled data, using DC current sampled data before and after commutation failure as according to
According to, according to DC current during commutation failure occur it is improper rise to, the second order and more than order derivative of current data have apparent increase
Big feature carries out Singularity Detection using the Daubechies small echos with second order vanishing moment to DC current sampled data,
Method based on threshold value comparison judges the specific time point that direct-current commutation failure occurs, and reaches and eliminates normal condition and exchange system
System minor failure is quickly detected the purpose at the time point of commutation failure.
To verify the accuracy of this method, experimental result is as viewed in figures 5-8.
Fig. 5 is the testing result that three-phase ground failure causes commutation failure.Corresponding valve current waveform is shown in Fig. 2.Upper figure
Lines are dc current waveforms, are normal current waveform before t0, three phase short circuit fault, grounding resistance 100 Ω, t1 occur for the t0 moment
Commutation failure occurs for the first time for the moment, and second of generation commutation failure of t3 moment is from figure below as can be seen that at commutation failure point
Wavelet coefficient is significantly improved, and the wavelet coefficient of commutation failure point far surpasses the threshold value 0.15 of this example, commutation failure twice
Point is accurately detected.
Fig. 6 is No. 2 valves and the current waveform of No. 6 valves and DC current when singlephase earth fault causes commutation, and Fig. 7 is inspection
Survey result.It is normal current waveform before t0, C phase short troubles, 70 Ω of grounding resistance occur for the t0 moment in Fig. 6.The t1 moment No. 2
Valve is connected again, and first time commutation failure occurs, and the t2 moment, No. 6 valves did not turned on, and DC current continues through No. 2 valve circulations, hair
Raw second of commutation failure.The commutation failure reason and t1, t2 at t3, t4 moment are similar.In Fig. 7, the wavelet systems of t1 to t4 moment
Much larger than other sampled points, and more than threshold value 0.15, commutation failure point is accurately detected number.
Fig. 8 is singlephase earth fault, and single fault degree is smaller, fails to draw testing result during direct-current commutation failure.Failure
Moment t0=1s occurs, impedance ground is 100 Ω of c phases, and at this time since fault condition is lighter, commutation mistake does not occur for straight-flow system
It loses.The dc current waveform under example, figure below are the wavelet coefficient of each sampled point to the upper figures of Fig. 8 thus, it can be seen that each point
Wavelet coefficient is more than threshold value, it can be determined that for commutation failure does not occur.
More than numerical results show to utilize treated waveform, the commutation of the danbechies small echos with second order vanishing moment
Wavelet coefficient is significantly improved at failed point, and wavelet systems during commutation failure do not occur with normal operation and ordinary failures
Number differentiation is apparent.This method singlephase earth fault relatively conventional to electric system and three-phase ground failure the most serious
It is applicable in, can show the specific time of commutation failure twice completely；Demonstrate the accuracy that this method puies forward power flow algorithm；This
Method calculates simply, can meet the needs in line computation, and management and running personnel is helped to find commutation failure at the first time, ensures
Electric power netting safe running.
Claims (2)
- A kind of 1. method for detecting direct current transportation commutation failure, it is characterised in that：This method is sampled by acquiring DC current Data are detected DC current sampled data, so as to judge the specific time point of direct-current commutation failure generation, reach quick Detect the purpose at the time point of commutation failure.
- 2. a kind of method for detecting direct current transportation commutation failure according to claim 1, it is characterised in that：The method is By acquiring DC current sampled data, using DC current sampled data before and after commutation failure as foundation, during according to commutation failure DC current occur it is improper rises to, the second order and more than order derivative of current data have the feature significantly increased, using with The Daubechies small echos of second order vanishing moment carry out Singularity Detection, the method based on threshold value comparison to DC current sampled data Judge at the specific time point that direct-current commutation failure occurs, to reach and eliminate normal condition and AC system minor failure, it is quick to examine Measure the purpose at the time point of commutation failure.
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Cited By (2)
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| WO2021009025A1 (en) * | 2019-07-12 | 2021-01-21 | Rheinisch-Westfälische Technische Hochschule (Rwth) Aachen | Method for detecting a short-circuited line in an electrical direct-voltage conductor network and device therefor |
| WO2021147772A1 (en) * | 2020-01-21 | 2021-07-29 | 华南理工大学 | Dc converter valve state detection method based on port current sequence characteristics |
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| WO2021147772A1 (en) * | 2020-01-21 | 2021-07-29 | 华南理工大学 | Dc converter valve state detection method based on port current sequence characteristics |
| US11959976B2 (en) | 2020-01-21 | 2024-04-16 | South China University Of Technology | DC converter valve state detection method based on temporal features of converter terminal currents |
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